The present invention relates to a substrate drying method and apparatus in which surfaces of substrates are dried by removing the substrates, immersed in pure water, from the pure water.
Conventionally, in such a drying apparatus as disclosed in Japanese examined Patent Publication No. 6-103686, IPA (Isopropyl Alcohol) is supplied as vapor, by using nitrogen gas as a carrier, into an upper space in a treatment tank of wafers, which are one example of substrates, treated with an etching solution and then washed with pure water. Then, the wafer surfaces are dried by draining the pure water in the treatment tank from a bottom portion of the treatment tank to expose the wafers in the treatment tank, and replace water droplets attached to surfaces of the exposed wafers with IPA vapor supplied into the upper space of the treatment tank.
Furthermore, there is also a drying apparatus in which, instead of exposing wafers in a treatment tank by draining pure water in the treatment tank from a bottom portion of the treatment tank, the wafers are dried by exposing the wafers in the treatment tank by raising the wafers from the treatment tank, and replacing water droplets attached to surfaces of these exposed wafers with IPA vapor supplied into an upper space of the treatment tank.
However, in the apparatus having the above structure, particles generated when the wafers are washed with pure water float in a vicinity of a liquid level of the pure water in the treatment tank. Since the wafers are exposed in the treatment tank by draining the pure water in the treatment tank from the bottom portion of the treatment tank, this drainage is successively performed from the pure water in the vicinity of the bottom portion of the treatment tank, and the pure water in the vicinity of the liquid level, in which the particles float, is finally drained. Therefore, a problem arises in that these floating particles are attached to wafer surfaces when the wafers are exposed from the liquid level.
Furthermore, in the apparatus having the above structure, since the wafers are exposed by draining the pure water from the bottom portion of the treatment tank, the pure water at the liquid level in the treatment tank is only finally drained, and hence a dissolution amount of IPA is increased at the liquid level with time. Therefore, an IPA concentration in the pure water at the liquid level and a thickness of a layer in which IPA is dissolved are increased, thereby degrading replacement efficiency. Thus, a problem arises in that drying efficiency is degraded, and non-uniform drying of the wafer surfaces occurs.
Furthermore, even when the wafers are exposed by raising them from the liquid level of the pure water in the treatment tank, a problem arises in that particles are similarly attached to wafer surfaces. Furthermore, there is a problem in that non-uniform drying of the wafer surfaces occurs because a wave is produced at the liquid level of the pure water upon raising of the wafers.
Accordingly, an object of the present invention is to provide a substrate drying method and apparatus in which, upon exposure of substrates from pure water, an amount of particles attached to surfaces of the substrates can be reduced, increases in a concentration of IPA dissolved in the pure water at a liquid level and a thickness of a pure water layer in which IPA is dissolved can be prevented, and drying efficiency of substrates can be improved to prevent non-uniform drying, and thus solve the above problems.